Surface engineering of γ-Al₂O₃ nanosheets with highly dispersed poly(ionic liquids) for selective CO₂ adsorption

An efficient CO₂ adsorbent (γ-Al₂O₃ @PAVIMBr) was constructed by means of graft copolymerization with mesoporous γ-Al₂O₃ nanosheets served as the host material and amino-functionalized imidazolium based poly(ionic liquids) (PAVIMBr) as the guest material. Thereinto, mesoporous γ-Al₂O₃ could provided abundant hydroxyl groups for loading PAVIMBr uniformly via chemical bonding interaction, while PAVIMBr was able to tailor suitable pore size and expose amino-groups adsorption active sites that was contributed to chemisorb with CO₂. It was observed that the general topography of γ-Al₂O₃ @PAVIMBr composite was almost unchanged after PAVIMBr loaded, and its mesoporous structure and crystalline form was still maintained. Moreover, the content of PAVIMBr in our composite could be calculated from the TGA results before and after its grafting. The obtained γ-Al₂O₃ @PAVIMBr presented a good CO₂ adsorption performance, its CO₂ adsorption capacity increased obviously. Meanwhile, the CO₂/N₂ selectivity of γ-Al₂O₃ @PAVIMBr was 15.3 times higher than that of γ-Al₂O₃ at room temperature and the pressure of 100 kPa, while the CO₂ uptake of γ-Al₂O₃ @PAVIMBr was almost 13 and 3 times higher than that of PAVIMBr and γ-Al₂O₃ at 10 kPa and 25 °C, respectively. It was mainly attributed to that the maintaining mesoporous channels in γ-Al₂O₃ @PAVIMBr could accelerate the CO₂ diffusion, while chemisorption of those exposed adsorption active sites from loaded PAVIMBr could improve the adsorption performance at lower CO₂ partial pressure and CO₂/N₂ selectivity of our composite. Furthermore, the excellent CO₂/N₂ selectivity, renewability and physicochemical stability of γ-Al₂O₃ @PAVIMBr might employ it as one of the potential CO₂ adsorbents.